The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art.
A mobile communication carrier can separate and operate a core network for each service for the sake of easiness of system operation and QoS (quality of service) protection. For example, a mobile communication system may be composed of two core networks. One is a dedicated core network which is dedicated to a specific service (for example, Internet of Things or IoT), and the other is a common core network used commonly for all other services. Operating a core network separately in this manner enables to efficiently support different requirements for each device and user. However, when a user terminal (User Equipment: UE) connects or attaches to the network, an appropriate core network needs to be selected based on the subscription information of the user terminal.
FIG. 1 is a flowchart of a conventional core network selection process.
Specifically, FIG. 1 shows, as a technology introduced by the 3GPP Release 13 standard, selecting a service-specific core network by using the service information (usage type) included in the subscription information when the user terminal attaches to the network for the first time. When a terminal 10 attaches to the network (Step S110), a base station (eNodeB) 20 cannot select a service-specific core network due to lack of information on the terminal. The base station 20 first selects a basic core network determined according to the setting, and transmits an attach request message (S112). A core network node ‘MME 1’ 30a that has received this message sends a location update request message to a home subscriber server (HSS) 40 (S114), and receives, from the HSS 40, a user's subscribed service information (UE usage type) (S116). When the attached core network does not support the subscribed service, the ‘MME 1’ 30a selects another core network ‘MME 2’ 30b that supports the subscribed service (S118). Then, in order to re-direct the terminal to the other selected core network, the ‘MME 1’ 30a sends a NAS request message to the base station 20 (S120). The subsequent process is the same as the conventional location registration (attach/tracking area update (TAU)) process.
The conventional method of selecting a core network needs a base station to first attempt to attach a terminal to a preset default core network, and then re-direct the terminal device to another core network, resulting in two attempted attachments. This increases the time for attachment and overhead disadvantageously. In addition, the conventional method provides the user with only a default type of service when the relevant network is not able to support the user's subscribed service, which prohibits efficient use of resources and impedes the improvement of user's QoS. Part of the deficiencies lies in the fact that a mobility management entity (MME) determines to select the core network and that only one service type is permitted for a single user.